Technical Field
The disclosure relates to a DC-DC converter.
Description of Related Art
In the related art, in a power conditioner for a power generation device such as a solar power generation device, a DC voltage of the power generation device may be boosted by a DC-DC converter, converted to an AC voltage by an inverter circuit, and output. FIG. 11 illustrates a circuit diagram of a general boosting chopper type DC-DC converter 50 that can be applied to the power conditioner as described above. This DC-DC converter 50 boosts an input voltage Vin using a boosting chopper 53. Magnetic energy is stored in a reactor 52, and the magnetic energy is converted into electric energy again and emitted, thereby boosting the input voltage. In the general boosting chopper type DC-DC converter (hereinafter simply referred to as a “boosting chopper”) 50 as illustrated in FIG. 11, the reactor 52 has a large influence on a device volume and cost, and therefore, a demand for miniaturization of the reactor 52 is increasing.
Here, a control scheme for a reactor current IL includes a continuous current mode (hereinafter also referred to as a CCM) and a discontinuous current mode (hereinafter also referred to as DCM). In the CCM, a part of a current waveform may have a negative value at a light load at which an average current is small, whereas the DCM is a mode in which a current waveform is a discontinuous waveform and a current does not have a negative value at the light load at which an average current is small. In the DCM mode, high efficiency can be obtained at the light load. Therefore, since high efficient driving can be performed with a smaller average current than that of the CCM by adopting the DCM, it is possible to miniaturize the reactor for boosting.
However, even when the DCM is adopted, it is difficult to greatly reduce a peak value of the current waveform even at the heavy load, and therefore, a switching element having a relatively large current capacity is necessary as the boosting chopper. Further, further miniaturization of the reactor is limited. This may hinder miniaturization and reduction in cost of the device.